Ornament of exceptional age incorporating representation of glory (8)
I believe the answer is:
gargoyle
'ornament' is the definition.
(gargoyle is a kind of ornament)
'exceptional age incorporating representation of glory' is the wordplay.
'exceptional' is an anagram indicator.
'incorporating' means one lot of letters goes inside another.
'representation of' indicates an anagram (I've seen this in other clues).
'age' is an anagram of 'gae'.
'glory' is an anagram of 'rgoyl'.
'gae' placed around 'rgoyl' is 'GARGOYLE'.
'of' acts as a link.
(Other definitions for gargoyle that I've seen before include "Ugly carved figure on a building" , "grotesque sight!" , "It drains off water" , "Spout ending in a grotesquely carved figure" , "Grotesque architectural statue" .)